Finite element modelling of superplastic-like forming using a dislocation density-based model for AA5083

Abstract

Superplastic-like forming is a newly improved sheet forming process that combines the mechanical pre-forming (also called hot drawing) with gas-driven blow forming (gas forming). Non-superplastic grade aluminium alloy 5083 (AA5083) was successfully formed using this process. In this paper, a physical-based material model with dislocation density and vacancy concentration as intrinsic foundations was employed. The model describes the overall flow stress evolution of AA5083 from ambient temperature up to 550 °C and strain rates from 10−4 up to 10−1 s−1. Experimental data in the form of stress–strain curves were used for the calibration of the model. The calibrated material model was implemented into simulation to model the macroscopic forming process. Hereby, finite element modelling (FEM) was used to estimate the optimum strain-rate forming path, and experiments were used to validate the model. In addition, the strain-rate controlled forming was conducted for the purpose of maintaining the gas forming with an average strain rate of 2 × 10−3 s−1. The predicted necking areas closely approximate the localized thinning observed in the part. Strain rate gradients as a result of geometric effects were considered to be the main reason accounting for thinning and plastic straining, which were demonstrated during hot drawing and gas forming by simulations.

Enhancement in the Modeling of Temperature and Strain Rate‐Dependent Plastic Hardening Behavior of a Sheet Metal

“…Note that prediction using KHL model for SHPB test data shows saturated hardening behavior at e P ! 0.02 (see Figure 8b Similar mechanical response was observed in other aluminum alloy, AA5083 in the study by Liu et al [32] In their work, AA5083 specimens were tested through uniaxial tension experiment under various temperature (%25-550 8C) and strain rate conditions (%10…”

Flow-Stress Model of 300M Steel for Multi-Pass Compression

“…where A i , n i , Q i were material constants. Then, the flow-stress (σ i ) was calculated by the Taylor equation [25]:…”

The Mechanics of Superplastic Forming - How to Incorporate and Model Superplastic and Superplastic-Like Conditions

“…The material and process was chosen similar to [1,2], however, to make the study clearer, it was limited with deviation from the SP range only in terms of strain rate; temperature and microstructure were set to be optimal (900°C - Fig.2b, and 8µm fine grained microstructure) . To extend the range of the validity of the analysis, the data set was extended to include that cited by Seshacharyulu et al [8,9,10]; Fig.…”

“…under SP conditions where grain boundary sliding predominates and under faster rate non-SP conditions where slip will tend to be of greater significance. There have been previous attempts at this [2] that have used a crystal plasticity type approach and attempted to build models based on a range of factors including knowledge of slip mechanisms, vacancy concentrations, diffusion rates, back-stresses, etc. Such models are mathematically complex and require the determination of a wide range of parameters and though they may appear to be scientifically rigorous the fact is that they make many assumptions regarding the balance of deformation process operating within some particular deformation space.…”